Method of applying silicate to wet asbestos-slag cement sheets after formation but prior to consolidation of such sheets



O 6 9 9 GROSS REFERENCE EXAMINER 30, 1966 JULIE CHI-SUN YANG 3,269,888

METHOD OF APPLYING SILICATE T0 WET ASBESTOS-S CEME F'IE SHEETS A R FORMATION BUT PRIOR TO C OLIDATION SUCH ETS I Filed Dec. 1963 INVENTOR. UL IE ill-J54! ATTOK/VEV Julie Chi-Sun Yang,

United States Patent 3,269,888 METHOD OF APPLYING SILICATE TO FOR- PRIOR TO CONSOLIDATION OF Somerville, NJ., assignor to Johns- Manville Corporation, New York, N.Y., a corporation of New York Filed Dec. 24, 1963, Ser. No. 332,998 7 Claims. (Cl. 162-119) This invention relates to the manufacture of asbestoscement products, and more particularly to an improved means for the manufacture of asbestos-cement products comprising hydraulic setting slags and the products thereof.

The relatively low cost of asbestos-cement materials and the effective and economical forming processes or techniques for the production of asbestos-cement products together with the outstanding physical properties of the resulting articles such as high strength and inorganic composition with their inherent resistance to the elements, etc., has resulted in the extensive utilization over the years of asbestos-cement materials and procedures for the manufacture of a variety of common products therefrom including, for example, pipe or conduit, building boards or sheets for siding, sheathing, interior walls and finishes, furniture, etc., and shingles for roofing or'siding, among numerous other applications. Typical compositions or furnishes for the commercial manufacture of products of I this category substantially exclusively comprise the common Portland type of hydraulic setting cements as the only or the principal cementitious binder component or phase. This substantially exclusive use of the Portland type hydraulic cement is apparently primarily due to its fast hydration and relative high early or initial strength characteristics which are more consonant and amenable to conditions or requirements of the conventional or most commonly utilized asbestos-cement manufacturing process comprrsrng the so-called Hatschek or wet process technrque.

Briefly, this common asbestos-cement manufacturing process involves d i s p gsing the asbestos and cement, etc., furnish materials in a water medium providing a dilute slurry, gollgpting or depositing the solids content from the slurry in the form of a gjr w et sheet and superimposing or building up layersthereofllpononeanotherand .consglrdating the composite rnass tointegratejhe layers and prov de a product of apt thickness andgensity. This type of process is illustrated by-th Hatschek U.S. Letters Patent No. 769,078 and Reissue 12,594, and more recent techniques and/or means therefor by US. Letters Patent No. 2,182,353, No. 2,246,536, and No. 2,322,592.

The relatively fast hydration and setting rate of the Portland type of cements and their high early or initial strength have comprised a major factor in the commercial application of asbestos-cement products in enabling the low cost production of asbestos-cement articles including pipe and other intricately shaped items by means of conventional wet process machines and techniques at high economically feasible forming machine and handling speeds or production rates with high product recovery,

including the initial forming or shaping of the item on an accumulator roll or mandrel followed by the prompt removal of the material therefrom substantially without deformation, s g, warpage, etc.

WET

Slag cements, or more specifically the common class of hydraulic setting cements prepared from or incorporating major proportions of granulated, finely divided blast furnace slags or modifications thereof, are markedly superior in resistance to acids and generally to chemicals and aggressive soils or environmental conditions over Portland type cements, as well as being substantially lower in costs. However, notwithstanding such advantages, this class of cements had not heretofore been found suitable for the commercial or economical production of asbestoscement articles when employed with common wet process forming means and techniques due, among other reasons, to their inherent tendency to sag or otherwise deform out of shape during production and handling.

It is the primary object of this invention to provide an effective and economical means of producing asbestosslag cement products.

It is also a primary object of this invention to provide means of utilizing finely divided hydraulic setting slags in the conventional manufacture of asbestos-cement products utilizing common wet process forming machines and techniques.

It is a further object of this invention to provide means of producing low cost, acid resistant asbestos-slag cement products having strength properties comparable to like asbestos-Portland cement products, and for manufacturing such products incorporating hydraulic setting slags as the principal cementitious binder utilizing substantially the same economically feasible conditions as in comparable asbestos-Portland cement methods.

It is a still further object of this invention to provide means of manufacturing pipe and the like hollow cylindrical bodies and conduit or containers from asbestoscement furnishes comprising hydraulic setting slags as the major cementitious or binder component wherein the green or uncured article or product such as a pipe section resists sag or deformation and maintains or preserves its s ape or configuration upon forming, in removal from the forming means such as a mandrel, and/or in subsequent handling when produced according to normal wet process means and conditions.

It is also an object of this invention to provide means of effectively and economically manufacturing low cost pipe and the like products from asbestos-cement furnishes comprising hydraulic setting slag as the predominant cementitious component which have high strength and acid resistance, and to provide the improved products thereof.

It is also an object of this invention to provide means of enabling the use of relatively low cost hydraulic setting slags in the manufacture of asbestos-cement products which in turn permits the utilization of greater proportions of silica in the stock and thereby furthering the savings in material costs, without any substantial degrading of physical and/ or chemical properties.

Other objects and advantages of this invention will be apparent from the detailed description given hereinafter, and it should be understood that the detailed description, while indicating preferred embodiments of the invention, is given by way of illustration only as variations and modifications within the spirit and scope of the invention will become apparent from the following detailed description.

The figure of the drawing comprises a schematic diagram illustrating a suitable means or device for the effective practice of this invention with a conventional wet process asbestos-cement forming machine and procedure.

Sodium silicate, of course, has heretofore been proposed for and/or utilized in the treatment of asbestos and/or cement materials as by adding a solution thereof to a suspension or slurry of asbestos and/or cement furnish or stock to induce or produce a number of varied effects including its application as a binder or adhesive, waterproofing material, flocculation agent, accelerator for the setting of cement, etc. For example, US. Letters Patent No. 1,872,480 shows the addition of sodium silicate as a flocculating agent to an asbestos-cement slurry to flocculate the cement. However, as with many other known additives, the utilization of sodium silicate with hydraulic setting cements and/or in asbestos-cement manufacturing processes, although sometimes effective in a particular function, entails undesirable and disadvantageous characteristics or effects such as filling or clogging the porous felt belts utilized in the wet process in the manufacture of asbestos-cement products destroying the essential permeability of the belts and thereby rendering them useless, in accumulating and building up in concentration in the asbestos-cement wet process system and in turn adultering and/or degrading the products due to the adverse efiects of sodium silicate upon the strength of hydraulic setting cements, in general effecting erratic action or results in hydraulic setting cement compositions, corroding equipment, etc., among other deleterious results such as set forth in U.S. Letters Patent No. 2,987,407. Moreover, notwithstanding certain specific desirable or useful properties and effects known, and extensive investigations or expen'mentations with sodium silicate or the like materials in asbestos and/or cements, the disadvantages inherent in so utilizing sodium silicate have prohibited its application in commercial processes.

The present invention, on the other hand, comprises means of utilizing sodium silicate whereby highly useful and advantageous effects are derived therefrom without encountering or imparting the normal or inherent deleterious effects or results of this material such as a substantial reduction in strength of hydraulic cement products, the build up of concentration or accumulation thereof in the slurry or system and in turn clogging or plugging of the machine felt in conventional wet process machines, etc. Moreover, in addition to avoiding or eliminating the undesirable aspects of sodium silicate in hydraulic cement compositions, the means of this invention decidedly enhance or amplify certain useful and advantageous effects of sodium silicate over and beyond those heretofore derived therefrom to the extent of at least about a 20% up to about 50% increase in effectiveness as will be apparent from direct comparisons of means set forth hereinafter.

In general, this invention comprises the discovery that hydraulic setting slag cements can be utilized in asbestoscement compositions or furnishes in conventional wet process asbestos-cement manufacturing machines and procedures at economical and normal machine speeds or production rates and conditions while resulting in high recoveries of products having adequate physical properties comparable to those of typical like asbestos-Portland cement products and of enhanced chemical properties through the means of minor amounts of sodium silicate W? to the asbestosement ateria s w 1 e wet an at a m mama? ftrrirsfi am m mmmn mower ,dep tl1 or into a oFap imensions. More specifically, in 5W wet process asmt type machine or procedure to which this invention applies, the sodium silicate solution is applied to the wet sheetlike body or layer of stock materials formed by withdrawing and/or depositing the solids and entrained water from the slurry prior to the accumulation and integration thereof as by rolling or revolving the sheet or layer of materials upon themselves on a roll or mandrel, normally under pressure.

To facilitate its application and activity or effectiveness the sodium silicate agent is applied to the wet asbestoscement stock in the form of an aqueous solution, a medium which is compatible with the asbestos-cement system. Sodium silicate materials suitable for this application comprise any one of the commonvor commercial grades having, for example, sodium oxide to silica ratios ranging from about 1.60 to 3.75 mols of SiO per mol of Na O. The sodium silicate dissolved or dispersed in water in apt or handleable amounts, such as concentrations up to about 20% by weight, can be applied to the wet asbestos-cement furnish or stock in quantities or at rates to provide at least approximately 0.125, up to approximately 57 by weight of sodium silidate'iolids based upon the tom of the solids of the asbestos-cement furnish or stock including silica, fill;e r s, etc., and preferred amounts for typica ydraulic setting slag cement containing formulas are approximately 0.8 Ibo 1% of sodium silicate solids per solids of the furnish. Excesses of odium 'licate tend to oduce deleterious em s ren th and/or indu cin erratic setting simmefBre H l3 maEi WFmmmsnsarnrsnifs in excess of about 2% sodium silicate solids are normally unnecessary and possibly undesirable. Moreover, al-

though substantially any concentrations of sodium silicate and water can be utilized in practicing this invention since the wet asbestos-cemet furnish or stock normally contains an excess of water at the point of application, concentrations of less than about 1% of sodium silicate simply entail the addition of excesses of water which must be subsequently removed while concentrations in excess of about 20% of sodium silicate involve rather viscid solutions which may present difficulties in applications such as the clogging of spray equipment, etc. Typically suitable solution concentrations for most means of application and maximum ease of control comprise about 3 to 10% by weight of sodium silicate solids. Appropriate techniques or means of applying solutions of the sodium silicate agent include spraying mgw gr the ljk e f egd troughs or distributors, roll applications, gfiiiylonyentiona or ty,p1ca means or techniqugs gf addinggr feed; y gia n waggrefla a sm tntmfisauhm n t e concentration an or amount of solution can be effectively coordinated with the quantity of stock and/or ma-- chine speed or rate of formation. Preferred means consist of spray apparatus which provide an atomized or finely divided spray and permit or facilitate a controlled uniform application.

An example of an effective and preferred means or technique for applying a sodium silicate solution in a typical wet process asbestos-cement operation is the arrangement or system schematically diagrammed in the drawing. The illustrated system of the drawing and operation thereof are as follows. A dilute aqueous suspension or slurry, of for example about 10 to 20 parts by weight of water per part of solids of the asbestos-cement furnish or stock formulation, is provided and maintained in cylinder mold vat or tank 1. Cylinder filter mold 2, positioned partially submerged within vat 1, rotates while the water of the suspension or slurry, normally induced by the application of subatmospheric pressures within the cylinder mold, passes through the wire screen or forami nous facing the cylinder mold causing the deposition and retention of the solids phase or content of the aqueous suspension on the surface of the cylinder mold screen forming a thin sheet or layer thereon of the solids as shown at 3.

The rotating cylinder mold 2 is in continuous contact with a moving endless conveyor comprising a porous felt 4 and the asbestos-cement slurry solids retained on theface of the cylinder mold are continuously transferred to v mold 2 and the accumulating or forming roll 5, an appropriate means such as spray device 6, or other equivalent applicator, administers the sodium silicate solution to the wet sheet of stock. Following the application of the sodium silicate solution, the conveyor belt passes over a suction box 7 whereby the reduced pressures withdraw water from the wet sheet and in turn draw the sodium silicate down through the mass of the sheet of stock. Next, the conveyor continues carrying the still damp sheet of stock containing the sodium silicate into contact with the accumulating and forming roll or mandrel 5 where the sheet of stock is transferred from the moving conveyor felt to the roll and at the same time is spirally wound or convoluted upon the roll and/or itself forming a laminated body which is consolidated by pressure from press roll 8 integrating the layers into a monolithic-like mass.

The following examples illustrate the marked reduction in sag or deformation of green, unhydrated or unset asbestos-cement compositions comprising a hydraulic setting slag as the major cementitious component due to the means of this invention among other desirable and decided advantages thereof and the over-all effects of this means in relation to other or prior techniques, as well as preferred and typical procedures or means for the effective and economical manufacture of asbestos-cement pipe and the like products with conventional equipment and conditions from low cost formulations comprising hydraulic setting slags, and the improved, chemical resistant products thereof. It is to be understood that the specific techniques or means, conditions, materials and/or proportions thereof and asbestos-cement formulations are merely exemplary and not to be construed to limit the invention in any particular details recited in these examples.

To expedite and control the testing and evaluation of the means of this invention and to provide reproducible or like circumstances therefor, and for comparison with other agents, conditions, formulations, etc. of a degree of standardization and/ or regulation not practical or possible in many instances with large scale or production equipment, a standardized test was adopted for the development and exploration of this invention. This test, referred to hereinafter as the sag cake test and comprising the means of evaluating and obtaining the data and relative results set forth in certain of the following examples, was applied under identical conditions, and each illustration thereof set forth in the examples, unless specified otherwise, was performed pursuant to the following procedure.

SAG CAKE TEST The basic steps of this test are put into effect or carried out according to a predetermined time schedule as given, and an appropriate timing mechanism is employed in connection therewith. Initially, a dry, thoroughly mixed (10 minute agitation) 150 gm. sample of stock of the particular asbestos-cement formulation to be evaluated is prepared for each cake test, and added to 1000 milliliters of distilled water with the mixing thereof commencing immediately at :00 minutes. After mixing 1:00 minute, the wet admixture of stock is promptly transferred to a vacuum filter box measuring 3 in. x 8 in. and having a bottom perforated plate of like dimensions covered with filter paper, and at 1:15 minutes a vacuum is applied to the filter box. The vacuum should be such as to register 16 in. of mercury during removal of water and between 13 and 13.5 in. of mercury thereafter throughout the remainder of the filtering operation which continues for a duration of 3 minutes and 45 seconds. Upon withdrawal of the excess water a 25 lb. hand tamp is placed on the top of the cake for 10 seconds to smooth its upper surface, and at 5:00 minutes the vacuum is removed. In the 5:00 to 6:00 minute interval the cake is removed from the filter box and in the 6:00 to 6:30

minute interval the cake is weighed. From 6:30 to 7:05 minutes the cake is placed in a press and then consolidated at a pressure of 320 p.s.i. applied across the entire 3 in. x 8 in. cake surface over 10 seconds at a uniform rate of loading using 3 to 4 strokes to reach maximum load. The application of pressure should start at about 6:50 minutes with maximum load being reached at 7:00 minutes and maintained until 7:05 minutes. From 7:05 to 9:00 minutes the press cake is again weighed and then set up for the sag test.

Next, the cake is prepared for measuring its sag or deviation from horizontal under a given load by placing the 3 in. x 8 in. cake across anvils positioned at each end of a base sheet providing an intermediate 6 in. free span and with a releasable center support to hold the test cake horizontally across the span between the anvils before the test is started. A foot or base of a gauge micrometer with an added dead weight of 140.0 gms. is mounted centrally between the anvils and positioned on the upper surface of the sag cake. The micrometer reading is taken to determine the thickness of the cake and as a basis for the subsequent sag measurement. At 9:00 minutes the center support between the anvil holding the intermediate section of the cake is released and a reading on the micrometer taken at 10:00 minutes and/or at other subsequently specified intervals. This reading is subtracted from the initial reading giving the sag or deviation from the horizontal due to the combined weight of the cake itself and the load applied from the micrometer assembly.

Upon completion of the sag measurement the cake is removed from the tester and carefully straightened on a fiat plate and placed for 24 hours in a moisture cabinet held at :3 F. and at least 90% relative humidity. This is followed by 16 hours in an autoclave at p.s.i. saturated steam (337.8 F.). After the curing cycle the cake is cooled to room temperature and submerged for 24 hours in fresh water at 73i3 F., removed and the saturated cake weight determined in both air and water. Then the fiexural strength of the cake is determined in accordance with ASTM Specification C-223-55 on a suitable testing device having a test span of 6 in. and the breaking load recorded. Last, the broken cake is placed in a ventilated oven at 212 to 220 F. and dried for 48 hours, cooled in a desiccator and the dry weight determined for use in water absorption and density calculation.

Example I A series of samples of like asbestos-cement formulations comprising a hydraulic setting slag as the principal cementitious component, were evaluated and compared by submitting each to the above described sag cake test under varying conditions including a control sample with no sodium silicate treatment, the admixing of a solution of sodium silicate in with the aqueous slurry of the asbestoscement formulations or stock samples pursuant to the disclosures of the prior art, and pursuant to this invention, the pouring of a solution of sodium silicate over formed sag cake samples in the filter box while under vacuum to simulate the application of a solution of sodium silicate to the wet sheet on a forming machine prior to traversing the suction box and formation of the product on the accumulating roll or mandrel. The asbestos-cement stock formulation or slurry solids consisted. in each case of 20% b u v r 400 b wei si ica 10% 3 weight Portlan c m 1. v i0 set'tm slag. The sodium silicate was N duct of Philadelphia Quartz having a ratio 1(Na O) :3.22(SiO (a pro TABLE I.SODIUM SILICATE TRATEMEN T OF ASBESTOS-CEMENT AND EFFECTS OF THE APPLICATION Water Retention Sag Re- Percent Percent Num- Silica Filter Percent duced in Sag Re- Improve- Break Thiclr- Dry Percent Sodium Silicate 1 ber 01 Cement Time, Bag in Inches duced ment Over Load ness in Donand Method of Application Sam- Ratio Sec. Inches Over Over Silicate in Pounds Inches sity, pies Filtra- Press Control Control Stock poi.

tion Slurry Nomocglntrolm. 3 1.0-1 77 41 .9 28.7 .165 107.9 .298 83.7 0.5 s um s i stack slurry 3 1 .0-1 66 53.3 33.8 .112 0.53 32.0 104.4 .277 79 .8

1.0% sodium silicate in stock slurry 3 1 .0-1 57 57.9 36 .7 .079 0.86 52.0 102 .6 .288 76 .7 1.5% sodium silicate in Stock slurry 3 1 .0-1 65 58.9 38.1 .064 0.101 61.0 113.7 .318 75 .9 0.5% sodium silicate poured over formed sag c e 3 1.0-1 79 49.0 33.7 .075 0.090 54.5 33.0 109 1 .300 79.5 1.0% sodium silicate poured over formed sag cake 3 1.0-1 82 53.0 38.1 .056 0.109 66.0 29.0 117.1 .309 76 .6 1.5% sodium silicate poured over formed sag cake 3 1.0-1 75 55.6 39.5 .050 0.115 70.0 22.0 107.8 .316 75.9

1 Percent of sodium silicate solids based upon dry stock weight.

Although the admixing of the sodium silicate solution with the other materials into the stock slurry did impart improved resistance to deformation or sag, the application of the sodium silicate agent subsequently to the formed asbestos-cement cake under vacuum decidedly enhanced the treatment rendering it one-third more eifective at low concentrations which minimizes the possible deleterious effects of sodium silicate upon hydraulic cement compositions.

Moreover, the period of retaining the sodium silicate solution in admixture with the asbestos-cement slurry solids does not appear to have any significant effect upon this particular means of treatment as is demonstrated by the following data of Table II which negates time as a relevant factor in the comparison of the means of this invention with that of'the prior art. In these runs, 100 cc. of a solution of 1% N grade sodium silicate were used, and the asbestos-cement stock formulation consisted of 20% asbestos fiber, 40% silica, and 40% hydraulic cement composed of Portland cement and 85% hydraulic setting slag.

Accordingly, the retention period of the asbestoscement slurry containing the sodium silicate solution has no significant or appreciable eifect upon the degree of sag.

To more accurately simulate a conventional asbestoscement wet process machine procedure wherein the white water or liquid phase of the slurry is repeatedly recirculated carrying with it all dissolved matter and the concentration of soluble agents added accumulates or builds up frequently to the detriment of the process and/or machine, a further series of runs comprising such conditions was made with the respective filtrate(s) from each preceding run of that particular series being repeatedly reused for twenty sag cake tests along with a make-up comprising the addition of 100 cc. of a solution of 1.05% N grade sodium silicate. The series consisted of a control employing no sodium silicate, the admixing of the sodium silicate solution in the slurry of stock, and the pouring of the sodium silicate solution over the formed sag cake under vacuum, with the respective filtrates being reapplied and in the latter two series with the sodium sili- 40 cate make-up. The data of these runs is set forth in Table TABLE II.SODIUM SILICATE SOLUTION ADMIXED IN SLURRY OF ASBESTOS-CEMENT AND EFFECTS OF RETENTION UPON SAG Water Retention Num- Silica Filter Percent Break Thick- Dry 0.7% Sodium Silicate ber of Cement Time, Sag in Load ness in Den- Wet Mix Time Sam- Ratio Sec. Inches Pounds Inches sity,

pies Filtra- Press pct.

tion

1 Minute, standard 3 1. 0-1 76 45. 9 31. 1 134 100.4 290 8,3. 9 3 Minutes 3 1. 0-1 73 49. 0 33. 7 128 106. 3 296 82. 9 5 Minutes 3 1. 0-1 71 48. 9 32. 5 132 107. 1 298 82. 5 7 Minutes 3 1. 0-1 69 50. 4 33. 1 123 104. 1 299 82. 3

1 Percent of sodium silicate solids based upon dry stock weight.

TABLE 111.-SODIUM SILICATE TREATMENT OF ASBESTOS-CEMENT WITH RE METHOD OF APPLICATION III with the sag of each series given as the average sag for all 20 cakes tested.

USE OF FILTRATE AND EFFECTS OF Water Retention Sag Re- Percent Percent Num' percent duced in Sag Re- Improve- Dry Additive 1 bet Silica Filter Average Inches duced ment over Break Thick- Densber of Cement Time, Sag in over over Silicate in Load ness in ity, Sam- Ratio Sec. F1ltra- Press Inches Control Control Stock Pounds Inches pct. ples tion Slurry None-Control 20 1. 0-1 83 48. 0 31. 5 137 111. 2 287 84. 4 0.7% Sodium Silicate in stock slurry 20 1. 0-1 49. 3 32. 4 126 011 8 105. 9 292 83. 0 0.7% Sodium Silicate poured over formed sag cake under vacuum 20 1. 0-1 83 51. 9 32. 9 094 043 31. 5 25. 4 103. 2 291 82. 9

l Pereent of sodium silicate solids based upon dry stock weight added to filtrate for each subsequent run.

Example II The effect of sodium silicate upon hydraulic cement compositions typically being erratic and varying with the composition and/ or conditions, particularly with Portland cement with which it frequently exerts a deleterious influence, the effects upon asbestos-cement stocks having compositions of varying ratios of hydraulic setting slag cement and Portland cement within the scope of this invention due to the treatment of this invention in relation to the admixing of the sodium silicate agent with aqueous slurries of the asbestos-cement stocks are illustrated in the following table. The stock formulation, other than the sodium silicate solution which comprised 100 cc.

of a solution of 1.05% N grade sodium silicate per cake suggested in the literature to exert various eifects upon hydraulic setting cements, when applied by assorted techniques including the means of this invention, are compared with asbestos-hydraulic setting slag and Portland cement furnishes and with a standard asbestos-Portland cement furnish such as is employed in many commercial asbestos-cement products. The slag containing asbestoscement formulations employed in these runs consisted of asbestos fiber, 40% silica, and 40% hydraulic setting cement of the given ratios of slag and Portland cement, and the standard asbestos Portland cement furnish formulation was 20% fiber, silica, and 50% Portland cement. The materials and conditions of these tests and the results thereof are as shown in Table V.

TABLE IV.-SODIUM SILICATE TREATMENT OF ASBESTOS-CEMENT COMPRISING VARYING PROPERTIES OF HYDRAULIC BINDERS AND EFFECT OF METHOD OF APPLICATION Sag in Inches Sag in Inches tor Sodi- Diflerence in Reduction oi Percent Improvement Slag-Portland Cement Mix tor Sodium Silium Silicate Poured Slag irom Silic ate Poured oi Invention over cate in Stock over Formed, Sag over Formed Cake in Silicate in Stock Slurry Cake under Vacu- Relation to Silicate in Slurry um Stock Slurry s57 slag 157 Portland.. 152 .107 29.6 15 72 slag: 2573 Portland 145 .114 031 21. 4 65% slag, Portland 182 095 087 47. 8 55% slag, Portland 189 089 100 52. 9 45% slag, Portland 173 095 038 9 1 Percent by weight oi total hydraulic setting cement components. test, was 20% fiber, 40% silica, and 40% hydraulic cement of the given slag and Portland ratios. Four sag 30 cake samples were employed in each test and the data represent the average thereof.

Example IV An example of the sag of a standard asbestos-Portland cement formulation and of a typical asbestos-slag containing cement composition in relation to that of the TABLE V.-EFFECTS OF SODIUM SILICATE AND RELATED HYDRAULIC CEMENT MODIFYING AGENTS UPON ASBESTOS-CEMENT COMPOSITIONS Cement Used Per- Additive Used Sag in Inches cent Composition Modulus of Mode oi Introducing Agent Rupture, Concenp.s.i. Slag Portland tration, Type 10 min. 30 min. min.

percent Run 1-... 25 2 (Jack Mix with water 0. 263 0. 195 0. 171 Run 20 1 0801:. 0.257 0. 209 0. 170 Run 3.--. 75 25 1 CeClz. do 0.220 0.157 0.136 Run 4 75 25 1 CaCh Pour Over cake in vacuum box 0. 353 0. 251 0. 259

before 25 lb. weight. 75 25 2 NaCl Mix with Water 0. 171 0. 0. 117 75 25 2 NaCl Pour over cake alter hand tamping. 0. 251 0. 252 0. 216 75 25 2 NaOH lit with Water 0. 459 0. 337 0. 221 75 .25 2 N aOH Mllillg'ltlhnivlfltel' increased vacuum 0. 211 0. 133 0. 060

e n. 75 25 2 NaOH-.. Pt i t ir over cake after hand tamp- 0.001

g 75 25 1 NaaCOr--- I 0 0. 058 80 20 1 NaiC0| .-c.o 0. 043 75 25 2 NaiCOi r n 0. 037 75 25 1 NaaSlOr -do 0. 016 75 25 2 NazSiOr--- d0 0. 006 0.046 0. 004 75 25 2 NaiSiOi Pt igr over cake alter hand tamp- 0.008 75 25 2 N arSiOu 0. 008 75 25 2 NarSiOr 0. 011 75 25 0. 5 Commercial solution 0. 036

sodium silicate. 75 25 2 0.010 75 25 1 0.075 75 25 0. 0. 048 75 25 0. 0.063 75 25 0. 0. 031 75 25 1. 0. 027 75 25 1 .-d0 0.017 Run 28 75 25 1 Commercial solution .d0 0. 061

sodium silicate. Run 29... 75 25 0. 088

1 15-minute sag because of the slow filtration rate. 2 All Portland cement (National). 3 All Portland cement (Keystone).

Example III The relative effects upon the sag of asbestos-cement composition of sodium silicate solutions and of solutions of other agents which could be presumed analogous to sodium silicate in this application and/or have been 75 position.

TABLE TL-COMPARISON OF SAG OF A STANDARD PORTLAND CEMENT ORMULATION WITH A TYPICAL SLAG WITHOUT AND WITH SODIUM F SILICATE TREATMENT l 100 cc. of a solution of 1% sodium silicate poured over sag cake in filter box. The reduction of sag in this instance due to the applicaand formed on the same equipment and under like condition of the treatment of this invention was approximately 30% over that of an identical slag formulation and an analogous Portland cement formulation.

The following examples illustrate the application of this invention to the manufacture of asbestos-cement pipe on a commercial scale employing conventional or standard wet process pipe forming machines, procedures and conditions including machine speeds and production rates.

Example V A plant scale run comprising the production of 24 in. diameter sewer pipe from a furnish consisting of 290 lbs. of asbestos fiber, 548 lbs. of silica, 137 lbs. of Portland cement, and 413 lbs. of hydraulic setting slag: was carried out under normal operating conditions with good formation and shape retention. The measurements, including deviations in cross sectional dimensions or sag, of this 7 pipe are given in the following table with comparable data for a standard asbestos-cement pipe 20 in. in diameter produced from a formula consisting of 225 lbs. of ashestos fiber, 450 lbs. of silica, and 465 lbs. of Portland cement tions. As the slag containing pipe was of a larger diameter its tendency to sag would normally be greater, but when this pipe was treated during formation by the application of a spray of solution of sodium silicate to the wet sheet of asbestos-slag and Portland cement slurry solids on the machine belt prior to the suction box and accumulation by wrapping about the forming mandrel for the fabrication of the pipe the larger diameter slag containing pipe sagged less than the smaller diameter standard Portland cement containing pipe. In this run the rate of of application of the sodium silicate spray to the slag containing pipe was 2.5 gals. per minute of a 7% solution which with a forming rate of about 200 lbs. of stock solids per minute equalled about 0.8% dry sodium silicate based on dry stock, or about 16 lbs. of sodium silicate per 2000 lbs. of stock. An inspection for out of roundness or sag and determination of the outside diameter of the standard 20 in. asbestos-Portland cement pipe and the sodium silicate treated 24 in. asbestos slag and Portland cement pipe resulted in the following data.

TABLE VIL-COMPARISON 0F SAG OF A STANDARD PORTLAND CEMENT WITH SODIUM SILICATE TREATED SLAG CEMENT CONTAINING Center of Section Number of Pi Sections Inspection Pro need Minimum Maximum Out 01 O.D., in. O.D., in Roundness, in.

Standard asbestos-Portland cement pipe 20 inches diameter:

1 (Standard) Passed 21. 67 21. 95 28 2 (Standard Rejected 21.37 21.90 .53 3 (Standard;... Passed 21.45 21.95 .50 4 (Standard) -.dO 21. 21. 87 22 5 (Standard) do 21. 68 21. 17 6 (Standard) do 21. 65 21. 92 27 Average (6 pipe) 33 Silicate treated asbestos-slag and Portland cement pipe, 24 inches diameter:

Average p p .28

1 Oval. 3 Damaged.

I I l l TABLE VIII.-CRUSH STRENGTHS OF 14 cement consisting of 75% hydraulic setting slag and the formation satisfactory. The standard asbestos-Portland cement pipe fu'rnish consisted of 20% asbestos fiber, silica, and Portland cement, and the asbestosslag cement furnishes of the special runs consisted of 20% STANDARD PORTLAND CEMENT PIPE AND SODIUM SILICATE TREATED SLAG CEMENT CONTAINING PIPE Wall Inside Break Modulus of Dry Density Number of Pipe Sections Tested Thick, Diameter, Load, Rupture, Lbs/Cu. Ft.

inches inches Lbs. p.s.i.

Standard asbestos-Portland cement pipe,

20 inches diameter:

1 (Standard)- .89 19. 93 3, 500 7, 400 107. 5 4 (Standard)- 89 19. 3,150 6, 620 109. 4 6 (Standard)- 84 19. 950 6, 940 107. 9

Average 87 19. 92 3, 300 6, 987 108. 3

Silicate treated asbestos-slag and Portland cement pipe, 24 inches diameter:

5 (Sla 1. 15 23. 94 5, 050 7, 670 105. 0 9 (Slag) 1. 15 23.93 4, 750 7, 200 106. 5

Average 1. 15 23. 93 4, 900 7, 435 105. 8

Example VI ticularly strength properties, of hydraulic cements. 35

asbestos fiber, 40% silica, and 40% hydraulic setting Portland cement. When employed, sodium silicate was applied as a spray of 1% solution at a rate of 2.5 gals. per minute. Curing the pipe was carried out by a 16 hour retention period indoors followed by wetting down and steam autoclaving at p.s.i. for 16 hours. The production and strength data for 6 in. pipe produced first from a standard Portland cement formulation, then a slag containing cement formulation, followed by a silicate treated slag containing cement formulation prior to returning to the standard Portland cement formulation of the given compositions and conditions are as follows:

TABLE IX.-RELATIVE STRENGTH PROPERTIES OF STANDARD PORTLAND CEMENT PIPE AND SLAG CEMENT CONTAINING PIPE BOTH UNTREATED AND SODIUM BILICATE TREATED Standard Special Special Special Standard Alter Before Run A Bun B Run 0 Special Run 8 ecial Run N o Silicate No Silicate Silicate N 0 Silicate o Silicate Spray Routine Recovery:

No. of sections inspected 119 67 54 73 189 Ins ction rejects, ovaL. 7 1 0 0 0 'fhin wall 0 l 0 0 0 Bad machining 0 2 0 0 0 Broke on lathe 1 0 0 0 0 Damage wet 0 0 1 0 0 Equipment iailur 0 0 1 0 0 Total inspection rejects 8= 6. 2=3. 6% 0=0. 0% 0:0. 0% Flexure rejects =0. 0% 1= 1.5% 3= 4% 0=0. 0% 0=0. 0% Hydrostatic rejects 2=1. 7% 3.0% 0= 0% 0% 0% Total rejects 1st time through.-. 0=8. 4% 7=11. 4% 5:8. 9% 0=0 0% 0 0 0% Ultimate Strength Tests:

No. of hydrostatic tests 10 9 7 10 Maximum MR, lb./in 4, 810 4, 150 4, 280 4, 040 4, 210 Minimum M R, 1b.] 3, 10 3, 730 3, 570 3, 430 3, 900 Average MR, 1b./in 4, 3, 980 3, 760 3, 850 4, 100

No. of Flexure Tests 10 9 7 8 11 Maximum MR. lb./in.. 4, 250 3, 870 3, 890 4, 020 4, 370

Minimum MR, lb./in. 3, 660 3, 4 0 3,150 3, 600 3, 570

Av3rage MR, lb.lin. 950 3, 610 3, 560 3, 790 3, 900

No. 0! Crush Tests 19 9 7 3 11 Maximum MR, lbJinfl- 8, 020 7, 800 6, 840 7, 800 8, 100

Minimum MR, lb./in. 930 250 6, 360 6, 640 6, 920

Average MR, Ila/in. 7, 430 7, 1 6, 620 7, 210 7, 590

Nevertheless, this data demonstrates that although the slag containing products of this invention are in general insignificantly lower in strength than corresponding Portland cement products, the sodium silicate treatment as applied according to this invention does not impart or result in discernible strength reductions or other deleterious effects. In all manufacturing runs from which this data was derived the production rates were normal and 75 Example VII The sag and strength of 8 in. diameter pipe produced 70 from a hydraulic setting sl-ag containing formulation both without and with the sodium silicate treatment of this invention were evaluated and compared with the like properties of pipe produced from the same hydraulic setting slag containing formulation when treated with sodium carbonate and a standard Portland cement formulation. These tests produced the data of the follow- Slag containing pipe with sodium silicate spray:

ing tables. The slag cement pipe was formed from a Average impact strength, ft.-lb. 0.650 stock slurry of 20% asbestos fiber, silica, 10% Standard deviation, ft.-lb. 0.064 Portland cement, and 30% hydraulic setting slag, and 5 Range, ft.-lb. 0.530-0.720 the Portland cement pipe was formed from a stock slurry Moisture content percent dry weight 1.51 of 20% asbestos fiber, 30% silica, and Portland. Slag containing pipe without sodium silicate spray:

The relative sag of the 8 in. pipe produced from these Average impact strength, ft.-lb. 0.601 formulations was determined by measuring the inside Standard deviation, ft.-lb. 0.075 vertical diameter of a one foot long section of green 10 Range, ft.-lb. 0.470-0.740 or uncured pipe of the given age and upon applying a Moisture content percent dry weight 1.73

centered, vertical load of 33 lbs. per ft. perpendicular to the length of the Plpe sample then taking a second slag containing composition has the highest impact l measuremen} of the inside Yerfical diamiter of the strength and although the silicate spray adds little to the P sample i The resultmg sag data 15 sat forth 15 impact strength of the slag cement, viz., an increase of in the following table.

TABLE X.RELATIVE SAG OF PIPE FORMED FROM PORTLAND CEMENT AND SLAG CEMENT BOTH UNTREATED AND TREATED WITH SODIUM SILICATE OR SODIUM These tests indicate that the sodium slicate treated CARBONATE.

I.D. Before I.D. Alter Diflerence Age of Wall Phase Load, Load, Pipe, Thickness,

Inches Inches Inches Hours Inches Portland cement, no treatment 7. 84 6. 1. 09 1% 0. 37 Slag cement, no treatment 7. 93 7. 74 0. 19 2 0. 38 Slag pip 2% solium silicate spray treatment durin manufacture 7.91 2% 0.34 Slag pipe, 1 0 sodium carbonate spray treatment during manufacture 7. 83 1 0.37

1 Collapsed.

When tested for strength characteristics pipe of the from 0.601 per lb. to 0.650 per 1b., the treatment does foregoing formulations, cured under identical conditions, 30 reduce the variability in impact strength as is indicated exhibited the following strength characteristics: by the lower standard deviation and range.

TABLE XI.RELATIVE STRENGTH PROPERTIES OF STANDARD PORTLAND CEMENT PIPE AND SLAG giklgggfqOgTAINING PIPE BOTH UNTREATED AND TREATED WITH SODIUM SILICATE OR SODIUM Form Time Hydrostatic Flexure Normal Saturated Density, Water Ab- Phase (sec.) MR (p.s.i.) MR (p.s.l.) Crush MR, Crush MR, pct. sorption,

p.s.i. p.s.i. percent Slag, min 79 3, 760 3, 790 7, 730 7, 530 96. 7 24.0 2% Sodium, max. 97 4, 750 4, 780 8, 670 8, 100 100. 4 26.0 Silcate spray, avg 89 (1'2) 4, 400 (6) 4, 360(7) 8, (7) 7, 820 (4) 98. 7 (4) 25. 0 (4) Slag, min 70 3, 850 4, 100 6, 560 No spray, max 83 3, 880 4, 230 7, 080

Avg 76(7) 3, 870 (2) 4, (2) 6, 820 (2) 7, 550(1) 102. 3(1) 22. 7(1) Slag, min. 73 4, 120 3, 230 6, 790 1% Sodium, max 82 4, 650 3, 900 7, 920 Silicate spray, avg 77(7) 4, 400 (4) 3, 610 (3.) 7, 400(3) 7, 590(1) 99. 4(1) 24. 4 (1) Standard, min 11 a, 790 4, 000 1, 320 a, 880 109. 1 17. 1 Portland, max--- 91 4, 720 4, 830 8, 660 7, 930 111. 4 19. 4 No spray, avg 85(26) 4, 120(11) 4, 500(12) 7,980 (11) 7, 360(11) 111. l (10) 18. 3(10) Slug, min 74 3, 580 3, 960 6, 460 105. 9 19. 9 No spray, max. 91 3, 920 4, 390 6, 890 106. 6 20.1

Avg 78(6) 3, 750(2) 4, (2) 8, 030(1) 6, 680(2) 106. 3(2) 20. 0(2) Slag, min 51 2, 360 2, 600 6, 670 6, 110 98. 2 21. 0 1% Sodium, mar.-- 85 3, 680 3, 770 7, 350 6, 850 104. 0 24. 4 Carbonate, avg 63 (23) 3, 050(11) 3, 310(10) 6, 660(9) 6, (10) 102. 2(9) 22. 1 (9) Norm: Figures in parentheses are number of pipe samples tested.

Bars measuring 10 in. 1: V2 in. x /2 in. were cut from selected samples of these pipes including the standard asbestos-cement pipe and the hydraulic setting slag containing pipe formed both without and with the sodium silicate spray treatment for impact strength tests. These tests produced the following:

TABLE XII.IMPACT STRENGTH DATA FOR STAND- ARD PORTLAND CEMENT -PIPE AND SLAG CEMENT CONTAINING PIPE BOTH TREATED WITH SODIUM Example VIII Additional runs comprising the manufacture of 8 in. diameter pipe of several compositions for a direct com- 5 parison of the elfects of the sodium silicate treatment upon the sag in each composition were carried out including the utilization of cements of different particle size. The formulations employed comprised as a standard a conventional Portland cement furnish of 20% as- SILICATE AND UNTREATED 70 bestos fiber, 30% silica, and 50% Portland cement, and Standard asbestos-Portland cement: for the hydraulic setting slag containing cements a fine Average impact strength, ft.-lb. 0.465 slag furnish of 20% fiber, 40% silica, 10% Portland, Standard deviation, ft.-lb. 0.080 and 30% slag having a Blaine classification of 5370 Range, ft.-lb. 0350-0600 crnF/gm. (St. Louis slag) and a coarse slag furnish of Moisture content percent dry weight 2.36 75 20% asbestos fiber, 20% Portland cement, and 60% slag having a Blaine fineness of 4470 cmF/gm. (St. Louis specific surface of approximately 4000 to 6500 cmF/grrn, slag). Eight inch pipe were produced from the foreand optimumly 4400 to 5400 cm. /-,gm., as derived by the going compositions and tested as in Example VII. Blaine test. Five exemplary hydraulic setting slag cement Namely, the inside vertical diameter of one foot long products produced from ordinary water quenched blast sample sections of uncured two hour old pipe was defurnace slags gave the following analysis:

A B C D E Ignition loss (at 1,000 F.) 0.47 0. .55 I 1. 7 S101 26. 7 27. 8 30. 3 34. 3 33. 3 0:10.. 45. 3 44. 3 41. 6 43. 1 39. 2 MgO-- 4. 2 3. 4 4. 1 6. 3 12. 3 AlzOr- 11. 8 12. 0 14. 4 10. 2 10. 7 T101 0. 56 0. 56 0. 54 0.4 0.28 F010;. 0. 83 1. 3 0. 86 2. 28 0. 72 P105- 0. 43 0.45 0. 10 0. 0. 009 N81 0. 56 0. 45 0. 34 0. 19 0. 19 K 0. 49 0.53 1. 1 0.19 0.17 Total SO 7. 5 6. 9 5. 92 0. 09 0. 22 0. 89 0. 91 0.95 1. 41 1. 2 Trace materials (B 0 BaO, M11303)- 0.3 0. 3 0.8

1 At 1,s00 F. termined both before and after the like application of a centered, vertical load of given weight per foot. The ing from the utilization of a hydraulic set-ting slag, includresults are given in Table XIII. ing the economics due to lower material costs and the TABLE XIII.RELATIVE SAG OF PIPE FORMED FROM PORTLAND CEMENT AND FROM FINE OR COARSE SLAG CEMENTS BOTH WITH AND WITHOUT SODIUM SILICATE Moreover, to achieve the maximum advantages result- I REATMENT Difference in Inside Diameter Number 01 After Load oi- Wall Thick- Pipe Composition Pipe and ness, Inches Average 11.86 lbs. 38.81 lbs.

Portland cement, no treatment 2 0.033 in 0.155 in 0. 61 Fine slag, no treatment 1 0.035 1.5 0. 58 Portland cement, 1% sodium silicate spray 2 0. 023.- 0.176 0.58 Fine slag, 1% sodium silicate spray 2 0.056 0.17 0.62 Coarse slag, 1% sodium silicate spray 2 0.026 0.138 0. 65

The strength characteristics of these pipe, upon air curincreased usage of silica in the stock formulation as well ing 24 hours and steam curing hours at 110 p.s.i. were as enhanced properties of the ultimate product such as as follows: greater chemical resistance, the slag cements should be TABLE XIV.RELATIVE STRENGTH PROPERTIES OF PIPE FORMED FROM PORTLAND CEMENT AND FROM FINE AND COARSE SLAG CEMENTS BOTH WITH AND WITHOUT SODIUM SILIOATE TREATMENT Form Time Hydrostatic Flexure MB MEX10, Normal Saturated Density, Water Pipe Composition (see.) MR (p.s.i.) (p.s.i.) p.s.i. Crush M'I, Crush MR, pct. Absorption,

p.s.i. p.s.i. percent Portland cement, min 48 4170 1 2. 69 7270 7320 109. 8 17, 3 No treatment, max--. 60 5500 6160 3. 32 0640 9060 111.5 19. 0

Fine slag, min 42 4100 4460 2.06 6300 5660 103. 1 l0. 3 No treatment, max 54 4 50 5260 2. 78 8880 7900 107. 4 20. 9

Avg 49 (26) 43 0(13) 2. 4003) 755003) 6700(13) 104. 7(11) 20, 3(11) Portland cement, min 38 2 090 2.15 6090 5660 99. 7 19, 7 1% Sodium silicate spray, max- 3450 5160 2. 74 9150 7660 107. 3 23. 3

Avg 7(28) 280003) (12) 2. 49(12) 7480(12) 6700(12) 104. 2(11) 21, 2(11) Fine slag, min 44 3 0 1.85 6690 5750 96. 6 21, 1 1% Sodium silicate spray, max 55 4560 5230 2. 32 8930 7370 102. 7 24. 3

Avg 8 (3 20 02) 4 (1 2. 11 (15) 769005) 6670(16) 99. 7 (16) 22. 7(16) Coarse, slag, min 50 3 3 10 2. 18 7250 6230 104. 5 19, 1 1% Sodium silicate spray, max- 69 4010 3990 2. 53 8440 7000 109. 2 21. 2

Avg 5 (22) 3 0( 3 10(1 2. 38(9) 7790(10) 6770(10) 106. 5(10) 20, 7(10) No'rE: Figures in parentheses are number of pipe in average.

The hydraulic setting slag containing compositions which comprise the major cementitious component or phase of the asbestos-cement formulations or stock utilof the over-all system, that is at least about 50 parts by ized in the practice of this invention comprise, for examweight of the hydraulic setting cementitious ingredients ple, granulated or quenched blast furnace slags or slags up to about 95 parts by weight thereof and preferably of similar metallurgical processes which are of a predomiabout to parts by weight, with the balance comnantly glassy nature or unoriented in structure, preferably prising portland cement, lime, or appropriate sources of containing no more than about 5% by weight thereof of lime. crystalline structure. To facilitate the hydration reaction, It will be understood that the foregoing details are these slags are preferably finely ground to a size having a 75 given for purposes of illustration and not restriction, and

employed as the major cementitious component or phase that variations within the spirit of this invention are to be included within the scope of the appended claims.

I claim:

1. The method of manufacturing asbestos-slag cement products comprising, dispersing an asbestos-hydraulic slag cement stock furnish in water forming a dilute aqueous slurry of the solids thereof, said hydraulic slag cement component of the stock furnish comprising at least approximately 50% by weight of hydraulic setting slag cement, forming a thin wet sheet of the slurry solids comprising the hydraulic cement'upon a porous member, applying an aqueous solution of sodium silicate to the thin wet sheet of slurry solids in amount of approximately 0.125% to 5.0% by weight of sodium silicate solids based upon the asbestos-hydraulic slag cement stock furnish solids content of the wet sheet, said application of sodium silicate solids being prior to consolidation of the said thin wet sheet whereby the sodium silicate solution is distributed throughout the same, superimposing layers of the wet sodium silicate containing sheet of slurry solids into a laminated structure and consolidating the laminated structure integrating the layers thereof.

2. The method of manufacturing asbestos-slag cement products comprising, dispersing an asbestos-hydraulic slag cement stock furnish in water forming a dilute aqueous slurry of the solids thereof, said asbestos-hydraulic slag cement stock furnish comprising asbestos fiber, silica, and hydraulic setting slag cement comprising approximately 50 to 95 parts by weight of hydraulic setting slag cement and approximately to 50 parts by weight of at least one source of lime selected from the group consisting of lime and Portland cement, forming a thin wet sheet of the slurry solids comprising the asbestos fiber, silica and hydraulic setting cement upon a porous member, applying an aqueous solution of sodium silicate to the thin wet sheet of slurry solids in amount of approximately 0.125% to 5.0% by weight of sodium silicate solids based upon the asbestos-hydraulic slag cement stock furnish solids content of the slurry, said application of sodium silicate solids being prior to consolidation of the said thin wet sheet whereby the sodium silicate solution is distributed throughout the same, removing the wet sodium silicate containing sheet of the slurry solids from the porous member, superimposing layers of the wet sodium silicate containing sheet of slurry solids into a laminated structure and consolidating the structure integrating the layers thereof.

3. The method of manufacturing asbestos-slag cement products comprising, dispersing an asbestos-hydraulic slag cement stock furnish in water forming a dilute aqueous slurry of the solids thereof, said hydraulic slag cement component of the stock furnish comprising at least approximately 50% by weight of hydraulic setting slag cement together with at least one source of lime selected from the group consisting of lime and Portland cement in amount of at least approximately 5% by weight thereof, forming a thin wet sheet of the slurry solids comprising the hydraulic setting cement upon a porous member, applying a spray of an aqueous solution of sodium silicate to the thin wet sheet of slurry solids in amount of approximately 0.5% to 2% by weight of sodium silicate solids based upon the asbestos-hydraulic slag cement stock furcement stock furnish comprising approximately 10 to approximately 30% by weight of asbestos fiber, approximately 20 to approximately by weight of silica and approximately 30 to approximately by weight of hydraulic setting cement consisting essentially of approximately 50 to approximately 95 parts by weight of hydraulic setting slag cement and approximately 5 to approximately 50 parts by weight of Portland cement, forming a thin wet sheet of the slurry solids comprising the asbestos fiber, silica and hydraulic setting cement upon a porous member, applying an aqueous solution of sodium silicate to the thin wet sheet of slurry solids in amount of approximately 0.125% to approximately 5% by weight of sodium silicate solids based upon the asbestos-hydraulic slag cement stock furnish solids content of the slurry, said application of sodium silicate solids being prior to consolidation of the said thin wet sheet whereby the sodium silicate solution is distributed throughout the same, superimposing layers of the wet sodium silicate containing sheet of the slurry solids into a laminated structure and consolidating the structure integrating the layers thereof.

5. The method of manufacturing asbestos-slag cement products comprising, dispersing an asbestos-hydraulic slag cement stock furnish in water forming a dilute aqueous slurry of the solids thereof, said asbestos-hydraulic slag cement stock furnish comprising approximately 10 to approximately 30% by weight of asbestos fiber, approximately 20 to approximately 50% by weight of silica and approximately 30 to approximately 60% by weight of hydraulic setting slag cement consisting essentially of approximately 50 to approximately 95 parts by weight of hydraulic setting slag cement and approximately 5 to approximately 50 parts by weight of Port-land cement, forming a thin wet sheet of the slurry solids comprising the asbestos fiber, silica and hydraulic setting cement upon a porous felt, applying a spray of an aqueous solution of sodium silicate to the wet sheet in amount of approximately 0.5 to approximately 2% by weight of the sodium silicate solids based upon the asbestos-hydraulic slag cement stock furnish solids content of the slurry, said application of sodium silicate solids being prior to consolidation of the said thin wet sheet, withdrawing water from the wet sheet of slurry solids with reduced pressures and thereby drawing the sodium silicate solution throughout the wet sheet of slurry solids, transferring the wet sheet to a roll, convoluting the wet sheet upon the roll under pressure consolidating the convoluted sheet and integrating the layers thereof.

6. The method of manufacturing asbestos-slag cement pipe comprising, dispersing an asbestos-hydraulic slag cement stock furnish in water forming a dilute aqueous slurry of the solids thereof, said asbestos-hydraulic slag cement stock furnish comprising approximately 20% by weight of asbestos fiber, approximately 30% to approximately 40% by weight of silica and approximately 40% to approximately 50% by weight of hydraulic setting slag cement consisting essentially of approximately to approximately parts by weight of hydraulic setting slag cement and approximately 15 to approximately 25 parts by weight of Portland cement, forming a thin wet sheet of the slurry solids comprising the asbestos fiber, silica and hydraulic setting cement upon a porous felt, applying a spray of an aqueous solution of sodium silicate to the wet sheet in amount of approximately 1% by weight of sodium silicate solids based upon the asbestos-hydraulic slag cement stock furnish solids content of the slurry, said application of sodium silicate solids being prior to consolidation of the said thin wet sheet, withdrawing water from the wet sheet of slurry solids with reduced pressures and thereby drawing the sodium silicate solution throughout the wet sheet of slurry solids, transferring the wet sheet to a roll, convoluting the wet sheet upon the roll under pressure consolidating the convoluted sheet and integrating the layers thereof, then autoclaving the thus produced asbestos-cement pipe.

2 7. The asbestos-slag cement product of the method of claim 1.

References Cited by the Examiner UNITED STATES PATENTS Bartlett 117-126 5 Piessevaux 162-265 Greider et a1. 162-184 Imnatd 162-265 Hatch et a1 117-126 10 22 2,350,030 5/ 1944 Greider et a1 117-126 2,791,159 5/1957 Lillis 162-154 3,173,831 3/1965 Pundsack et a1. 162-154 FOREIGN PATENTS 908,125 10/ 1962 Great Britain.

DONALL H. SYLVESTER, Primary Examiner.

S. LEON BASHORE, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3,269,888 August 30, 1966 Julie Chi-Sun Yang It is hereby certified that error appears in the above numbered patent/requiring correction and that the said Letters Patent should read as corrected below.

Columns 7 and 8, Table l, in the title for "TRATEMENT" read TREATMENT same Table I under Break Load Pounds for "109 1" read 109 1 column 11 line 41 for "465" read 645 columns 13 and 14 Table VIII under'Break Load Pounds for "3,300l read 3, 200 Table IX, first column under N0. of Flexuie Tests for "AvSrage MR, lb/in, read Average MR, lb ./in. 2 same columns Table IX, under Special Run C Silicate Spray, for "7 210" read 7 120 column 14 line 1, strike out "cement consisting of 75% hydraulic setting slag and 25%"; same column 14, between lines 24 and 25, insert cement consisting of 75% hydraulic setting slag and 25% Signed and sealed this 15th day of August 1967.

(SEAL) Attest:

EDWARD M.PLETCHER,JR, EDWARD J BRENNER Attesting Officer Commissioner of Patents 

1. THE METHOD OF MANUFACTURING ASBESTOS-SLAG CEMENT PRODUCTS COMPRISING, DISPERSING AN ASBESTOS-HYDRAULIC SLAG CEMENT STOCK FURNISH IN WATER FORMING A DILUTE AQUEOUS SLURRY OF THE SOLIDS THEREOF, SAID HYDRAULIC SLAG CEMENT COMPONENT OF THE STOCK FURNISH COMPRISING AT LEAST APPROXIMATELY 50% BY WEIGHT OF HYDRAULIC SETTING SLAG CEMENT, FORMING A THIN WET SHEET OF THE SLURRY SOLIDS COMPRISING THE HYDRAYLIC CEMENT UPON A POROUS MEMBER, APPLYING AN AQUEOUS SOLUTION OF SODIUM SILICATE TO THE THIN WET SHEET OF SLURRY SOLIDS IN AMOUNT OF APPROXIMATELY 0.125% TO 5.0% BY WEIGHT OF SODIUM SILICATE SOLIDS BASED UPON THE ASBESTOS-HYDRAULIC SLAG CEMENT STOCK FURNISH SOLIDS CONTENT OF THE WET SHEET, SAID APPLICATION OF SODIUM SILICATE SOLIDS BEING PRIOR TO CONSOLIDATION OF THE SAID THIN WET SHEET WHEREBY THE SODIUM SILICATE SOLUTION IN DISTRIBUTED THROUGHOUT THE SAME, SUPERIMPOSING LAYERS OF THE WET SODIUM SILICATE CONTAINING SHEET OF SLURRY SOLIDS INTO A LAMINATED STRUCTURE AND CONSOLIDATING THE LAMINATED STRUCTURE INTEGRATING THE LAYERS THEREOF. 